Water-blocking fireproof cable and preparation method thereof

Abstract

The invention relates to the technical field of cables, in particular to a water-blocking fireproof cable and a preparation method thereof.The water-blocking fireproof cable comprises a cable core, the cable core is formed by twisting at least two insulating wire cores, and the cable core is sequentially coated with a waterproof heat insulation layer, a water-blocking layer and an outer protection layer. The conductor stranding equipment is provided with the induction annealing unit, and the conductor is further annealed by the annealing unit after being stranded, so that the overall elongation of the conductor is improved by 15%; the ceramic silicone rubber composite tape is used for wrapping to form a compact protection layer, so that insulation falling is prevented, and the insulation stability, the fire resistance and the water resistance are better; the inorganic filler of the waterproof heat-insulating layer expands and carbonizes to form a heat-insulating barrier, so that the structural stability and fire resistance of the insulating wire core are ensured, and the waterproofness and the mechanical impact resistance are also improved; the waterproof layer adopts a double-layer water-blocking structure of a longitudinally-wrapped plastic-aluminum composite tape and a wrapped low-smoke halogen-free water-blocking tape, so that the requirements of environmental protection and long-acting water blocking are met; the waterproof fireproof cable is simple in structure and convenient to install and lay.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, in particular to a water-blocking fireproof cable and a preparation method thereof. Background Art

[0002] With the rapid development of power systems, the application of fire-resistant cables has gradually expanded from traditional indoor installations to complex environments such as underground rail transit, large industrial facilities, tunnels, and integrated pipeline corridors. In these scenarios, cables are often laid in cable trenches, directly buried, or in humid underground areas, and may even be partially or completely submerged in water for long periods of time. However, while fire-resistant cables offer excellent fire resistance, their insulation layers (such as magnesium oxide and mica tape) and metal sheaths (such as copper sheaths) can degrade in performance due to moisture penetration and electrochemical corrosion when immersed in water or in high humidity environments. This can even lead to insulation breakdown, seriously threatening the safe and stable operation of power systems.

[0003] Currently, conventional cable water-blocking measures use extruded polyethylene (PE) as a barrier layer, but this material cannot meet the low-smoke, halogen-free, and environmentally friendly performance requirements of fire-resistant cables. Therefore, given the unique operating conditions of fire-resistant cables in flooded environments, there is an urgent need to develop more reliable and durable waterproofing solutions to ensure safe operation throughout the cable's lifecycle. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the currently commonly used fire-resistant cables can only be used in indoor building fire protection systems. When laid outdoors in humid or water-logged environments, the insulation performance of their insulation layer and metal sheath may deteriorate due to moisture penetration, electrochemical corrosion, etc., and even cause insulation layer breakdown.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a water-blocking fire-proof cable, including a cable core, which is formed by twisting at least two insulating wire cores, and the cable core is sequentially covered with a waterproof and heat-insulating layer, a water-blocking layer and an outer sheath. The insulating wire core is twisted by a plurality of annealed copper monofilaments through a device equipped with an induction annealing unit, and the copper conductor is sequentially wrapped with an insulating layer and a wrapped protective layer.

[0006] Furthermore, its insulated wire core is protected by extruded ceramic silicone rubber insulation and wrapped ceramic silicone rubber composite tape. The silicone rubber material itself is water-resistant and moisture-resistant, and is not easily swollen or degraded after long-term immersion. Ceramic powder is added to the silicone rubber, and the particle size of the ceramic powder is controlled at 1~10um to ensure uniform high-temperature sintering and protect the conductor from normal power supply under flame.

[0007] Furthermore, the ceramic silicone rubber insulation adopts an extrusion process with an extrusion thickness of not less than 1.0 mm. Its material composition includes 40% methyl vinyl silicone rubber, 40% ceramic powder, 10% fumed silica, 5% nano-alumina, 3% silicone oil, 1% silane coupling agent, 0.5% platinum catalyst and 0.5% antioxidant; the obtained ceramic silicone rubber insulation material has the dual characteristics of room temperature silicone rubber elasticity and high temperature ceramic fire resistance, and is highly hydrophobic. After long-term immersion in water, the water absorption rate is less than 0.1% (much lower than the 1%~5% of mica tape and the 5%~15% of magnesium oxide powder).

[0008] Furthermore, the ceramic silicone rubber composite tape is overlapped and wrapped, with a wrapping thickness of 0.2-0.4 mm and a wrapping overlap rate controlled at 15%-20%. Because of its excellent self-adhesion, it can further block moisture and prevent mechanical damage to the insulation.

[0009] Furthermore, the waterproof and thermal insulation layer adopts highly filled silicone rubber refractory material with an extrusion thickness of 1.5~2.5mm, and an extrusion mold is used to evenly and efficiently inject the filler into the edge gap of the cable core. The increased density makes the waterproof and thermal insulation layer tightly combined with the cable core, ensuring the tightness and stability of the cable core structure.

[0010] Furthermore, the highly filled silicone rubber refractory material comprises 20%-30% methyl vinyl silicone rubber, 30%~50% silicon powder, 20%~35% mica powder, 10%~20% calcium silicate fiber, 5%~10% silicon dioxide, and 3%~5% silicone oil; the prepared highly filled silicone rubber refractory material has excellent water-blocking and moisture-resistant properties (water absorption rate is less than 1%), and the material expands in the flame to form a honeycomb ceramic layer for heat insulation and fire prevention, thereby further improving the fire resistance of the cable.

[0011] Furthermore, the water-blocking layer adopts a double-layer structure of longitudinally wrapped aluminum-plastic composite tape + wrapped low-smoke halogen-free water-blocking tape. The plastic film of the aluminum-plastic composite tape faces outward. The plastic film has good flexibility and moisture resistance, which can effectively take into account the waterproofness, durability and construction convenience of the cable. The water-blocking tape swells when it comes into contact with water and tightly covers the internal wire core, working together with the aluminum-plastic composite tape to fully guarantee the waterproof performance of the cable, ensuring that the cable can operate stably and reliably in humid or even water environments.

[0012] Furthermore, the outer protective layer adopts a cross-linked silane halogen-free low-smoke flame-retardant sheath with a thickness greater than or equal to 2.0 mm. The cross-linked silane halogen-free low-smoke flame-retardant sheath has excellent water resistance, flexibility, halogen-free, non-toxic and environmentally friendly properties.

[0013] Furthermore, the cross-linked silane halogen-free, low-smoke flame-retardant sheath material primarily consists of EVA / POE / TPU / silane crosslinker. EVA, with its excellent flexibility, chemical resistance, and processability, provides the sheath's fundamental physical properties. POE, with its excellent elasticity and weather resistance, enhances the sheath's aging resistance, making it less susceptible to cracking and deformation during long-term use. TPU improves the sheath's abrasion resistance and mechanical strength, enhancing the cable's protection under complex operating conditions. Silane cross-linking forms a three-dimensional network structure, improving long-term temperature resistance (up to 105°C). Furthermore, cross-linking reduces interstitial spaces between molecular chains, fundamentally reducing moisture permeability (water absorption rate less than 0.8%).

[0014] The present invention also provides a method for preparing the above-mentioned water-blocking fireproof cable, the steps of which are: S1: 99.99% high-purity copper rods are drawn and annealed on a copper drawing machine at high speed to produce oxygen-free copper wire. The oxygen-free copper wire (diameter 2.58±0.02mm) is twisted in three layers in opposite directions to form the copper conductor. S2: Extruding ceramic silicone rubber insulation from the copper conductor obtained in step S1 through a silicone rubber extruder and wrapping it with a ceramic silicone rubber composite tape by a wrapping machine to obtain an insulated wire core; S3: twisting the insulated wire cores obtained in step S2 into a cable, filling the gaps in the middle of the wire cores with low-smoke halogen-free water-blocking rope during twisting, and leaving the gaps at the edges unfilled, to obtain a cable core; S4: Extruding a highly filled silicone rubber refractory material through a silicone rubber extruder through the cable core obtained in step S3, and using an extrusion die to fully fill the gaps around the cable core to obtain a waterproof and heat-insulating layer; S5: longitudinally wrapping the waterproof and heat-insulating layer in S4 with an aluminum-plastic composite tape and a water-blocking tape to obtain a double-layer water-blocking layer; S6: A layer of cross-linked silane halogen-free low-smoke flame retardant sheath is extruded outside the water-blocking layer in S5.

[0015] In step S2, the ceramic silicone rubber insulation thickness is not less than 1.0 mm, and the ceramic silicone rubber composite tape thickness is 0.2 mm.

[0016] In step S3, the cable twisting pitch is controlled to be 22 to 26 times the cable outer diameter, and the wire cores are twisted tightly and not loose.

[0017] In step S6, the cross-linked silane halogen-free low-smoke flame-retardant sheath is not less than 2.0 mm.

[0018] The beneficial effects of the present invention are: (1) The conductor stranding equipment of the present invention is equipped with an induction annealing unit. After the conductors are stranded, they are further annealed in the annealing unit, so that the DC resistance of the conductors meets the requirements of the GB / T 3956 standard and the overall elongation of the conductors is increased by 15%; (2) The insulated wire core of the present invention is composed of extruded ceramic silicone rubber insulation and wrapped ceramic silicone rubber composite tape. The ceramic silicone rubber is based on organic silicone rubber and is added with high-temperature resistant ceramic fillers. It not only retains the excellent insulating electrical properties and waterproof properties of silicone rubber, but also significantly improves the fire resistance through the ceramic fillers. The ceramic silicone rubber composite tape is wrapped to tightly cover and protect the insulated wire core under high temperature of flame, forming a dense protective layer to prevent insulation from falling off. Compared with mica tape or magnesium oxide powder insulation, its insulation stability, fire resistance and water barrier properties are better. (3) The waterproof and heat-insulating layer of the present invention uses a highly filled silicone rubber refractory material, which is tightly coated with the insulating wire core through an extrusion production process. Under the high temperature of the flame, the inorganic filler expands and carbonizes to form a heat-insulating barrier, ensuring the structural stability and fire resistance of the insulating wire core. Compared with the traditional loose filling structure, the extrusion molding makes the waterproof and heat-insulating layer more tightly bonded to the wire core, and the waterproofness and mechanical impact resistance are also improved; (4) The waterproof layer of the present invention adopts a double-layer water-blocking structure of longitudinally wrapped aluminum-plastic composite tape and wrapped low-smoke halogen-free water-blocking tape. The inner layer of aluminum-plastic composite tape is bonded by hot-melt adhesive to form a completely sealed water-blocking layer, blocking liquid water and oxygen; the outer layer of low-smoke halogen-free water-blocking tape tightly wraps the inner layer and blocks water vapor from penetrating inward, taking into account both environmental protection and long-term water-blocking requirements; (5) The outer sheath of the present invention adopts a cross-linked silane halogen-free low-smoke flame-retardant sheath. The material adopts a cross-linked three-dimensional network structure to reduce the gap between molecular chains. The water absorption rate is less than 0.8%, which is 46% lower than the 1.5% of thermoplastic halogen-free material. The temperature resistance is improved to 105°C. (6) The water-blocking fireproof cable of the present invention has a simple structure and is easy to install and lay. It can be laid in complex environments such as humid, high-temperature, and corrosive environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and examples.

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] In the figure: cable core 1, copper conductor 11, insulation layer 12, protective layer 13, central filling layer 14, waterproof and heat-insulating layer 2, water-blocking layer 3, outer sheath 4. DETAILED DESCRIPTION

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0023] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0024] like Figure 1 As shown, a water-blocking fire-resistant cable of this embodiment includes, from the inside to the outside, a cable core 1, a waterproof and heat-insulating layer 2, a water-blocking layer 3 and an outer sheath 4. The cable core 1 is made of a copper conductor 11, an extruded insulating layer 12 outside the copper conductor 11, a wrapped protective layer 13, and a central filling layer 14.

[0025] During the processing of the ceramic silicone rubber insulation of the insulating layer 12, an extrusion process is adopted. Through high-pressure extrusion, the insulating layer is evenly wrapped around the surface of the copper conductor 11 and fills the twisted gaps, thereby improving the insulation reliability and fire resistance.

[0026] The protective layer 13 ceramic silicone rubber composite tape is wrapped around the surface of the insulating layer 12 in an overlapping manner, with an overlapping rate controlled at 15% to 20%, and the wrapping is smooth and wrinkle-free.

[0027] The copper conductor 11 is twisted with oxygen-free copper wire, and the central filling layer 14 is a low-smoke, halogen-free, water-blocking filling rope. When burned, the smoke density is low (transmittance ≥ 60%), and no halogen acid gas is released. The expansion rate can reach 300% to 400% when exposed to water.

[0028] The waterproof and heat-insulating layer 2 is a highly filled silicone rubber refractory material with a thickness of 1.5 to 2.5 mm. During its preparation, an extrusion production process should be adopted to tightly wrap the cable core 1 and fully fill the gaps along the edges of the cable core 1 to improve the density and water resistance and ensure the tightness of the cable core structure.

[0029] The water-blocking layer 3 is a double-layer structure of longitudinally wrapped 0.15mm aluminum-plastic composite tape + wrapped 0.2mm low-smoke halogen-free water-blocking tape, with the plastic film of the aluminum-plastic composite tape facing outward, which can effectively take into account the waterproofness, durability and construction convenience of the cable. The water-blocking tape expands when exposed to water and blocks the penetration channel.

[0030] The outer sheath 4 is a cross-linked silane halogen-free, low-smoke, flame-retardant sheath material with a thickness of no less than 2.0 mm. The main components of this material are EVA / POE / TPU / silane crosslinker. Compared to conventional low-smoke, halogen-free, flame-retardant polyolefin cable materials, silane crosslinking forms a three-dimensional network structure with long-term temperature resistance of up to 105°C. Crosslinking also reduces interstitial spaces between molecular chains, lowering moisture permeability (water absorption rate less than 0.8%).

[0031] The present invention also provides a method for preparing the above-mentioned water-blocking fireproof cable, the steps of which are: S1: 99.99% high-purity copper rods are drawn and annealed at high speed on a copper drawing machine to produce oxygen-free copper wires. The oxygen-free copper wires (diameter 2.58±0.02mm) are then twisted in three layers in opposite directions to form copper conductor 11. S2: The copper conductor 11 obtained in step S1 is extruded with a silicone rubber extruder to obtain ceramic silicone rubber insulation and then wrapped with a ceramic silicone rubber composite tape by a wrapping machine to obtain an insulated wire core; The insulated core is made of several annealed copper monofilaments twisted together using an induction annealing unit. This is a state-of-the-art heat treatment process that uses electromagnetic induction to alter the properties of metals. By precisely controlling the temperature, the metal exhibits enhanced ductility, reduced hardness, and increased toughness. This process rapidly heats and cools the material, minimizing internal stresses and preventing defects, making it particularly suitable for industrial applications requiring optimized metal properties. The thickness of the extruded insulation layer 12 is not less than 1.0 mm, and the thickness of the wrapped protective layer 13 is 0.2-0.4 mm; S3: twisting the insulated wire cores obtained in step S2 into a cable, filling the gaps in the middle of the wire cores with low-smoke halogen-free water-blocking rope during twisting, and leaving the gaps at the edges unfilled, to obtain a cable core; S4: The cable core obtained in step S3 is extruded through a silicone rubber extruder to extrude a highly filled silicone rubber refractory material, and an extrusion die is used to fully fill the gaps around the cable core to obtain a waterproof and heat-insulating layer 2; S5: longitudinally wrapping the waterproof and heat-insulating layer 2 in S4 with an aluminum-plastic composite tape and a water-blocking tape to obtain a double-layer water-blocking layer 3; S6: A layer of cross-linked silane halogen-free low-smoke flame retardant sheath is extruded outside the water-blocking layer 3 in S5; In step S2, the ceramic silicone rubber insulation thickness is not less than 1.0 mm, and the ceramic silicone rubber composite tape thickness is 0.2 mm.

[0032] In step S3, the cable twisting pitch is controlled to be 22 to 26 times the cable outer diameter, and the cores are twisted tightly and not loose; In step S6, the cross-linked silane halogen-free low-smoke flame-retardant sheath is not less than 2.0 mm.

[0033] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A water-blocking fireproof cable, comprising a cable core (1), characterized in that: The cable core (1) is formed by twisting at least two insulated wire cores, and the cable core (1) is sequentially coated with a waterproof and heat-insulating layer (2), a water-blocking layer (3) and an outer sheath (4). The insulated wire core is twisted by a device with an induction annealing unit provided on a plurality of annealed copper monofilaments, and the copper conductor (11) is sequentially extruded with an insulating layer (12) and a wrapped protective layer (13). The insulated wire core is insulated by extruded ceramic silicone rubber and protected by a wrapped ceramic silicone rubber composite tape. Ceramic powder is added to the silicone rubber, and the particle size of the ceramic powder is controlled to be 1-10 μm.

2. A water-blocking fireproof cable according to claim 1, characterized in that: The ceramic silicone rubber insulation adopts an extrusion process with an extrusion thickness of not less than 1.0 mm. Its material composition includes 40% methyl vinyl silicone rubber, 40% ceramic powder, 10% fumed silica, 5% nano-alumina, 3% silicone oil, 1% silane coupling agent, 0.5% platinum catalyst and 0.5% antioxidant.

3. The water-blocking fireproof cable according to claim 1, characterized in that: The ceramic silicone rubber composite tape is wrapped in an overlapping manner, with a wrapping thickness of 0.2-0.4 mm and a wrapping overlap rate controlled at 15%-20%.

4. The water-blocking fireproof cable according to claim 1, characterized in that: The waterproof and heat-insulating layer (2) is made of highly filled silicone rubber refractory material with an extrusion thickness of 1.5 to 2.5 mm.

5. The water-blocking fireproof cable according to claim 4, characterized in that: The high-filled silicone rubber refractory material comprises 20%-30% methyl vinyl silicone rubber, 30%-50% silicon micropowder, 20%-35% mica powder, 10%-20% calcium silicate fiber, 5%-10% silicon dioxide, and 3%-5% silicone oil.

6. The water-blocking fireproof cable according to claim 1, characterized in that: The water-blocking layer (3) adopts a double-layer structure of longitudinally wrapped aluminum-plastic composite tape + wrapped low-smoke zero-halogen water-blocking tape, wherein the plastic film of the aluminum-plastic composite tape faces outwards.

7. The water-blocking fireproof cable according to claim 1, characterized in that: The outer protective layer (4) adopts a cross-linked silane halogen-free low-smoke flame-retardant sheath with a thickness greater than or equal to 2.0 mm. The main components of the material of the cross-linked silane halogen-free low-smoke flame-retardant sheath are EVA / POE / TPU / silane cross-linking agent.

8. A method for preparing a water-blocking fireproof cable, comprising the following steps: S1: 99.99% high purity copper rods are used to produce oxygen-free copper wires through high-speed continuous drawing and undrawing on a copper drawing machine. The diameter of the oxygen-free copper wires is 2.58±0.02mm. The copper conductors (11) are obtained by three-layer reverse twisting and compaction. S2: Extruding ceramic silicone rubber insulation from the copper conductor (11) obtained in step S1 through a silicone rubber extruder and wrapping it with a ceramic silicone rubber composite tape by a wrapping machine to obtain an insulated wire core; S3: twisting the insulated wire cores obtained in step S2 into a cable, filling the gaps in the middle of the wire cores with low-smoke halogen-free water-blocking rope during twisting, and leaving the gaps at the edges unfilled, to obtain a cable core; S4: The cable core obtained in step S3 is extruded through a silicone rubber extruder to extrude a highly filled silicone rubber refractory material, and an extrusion die is used to fully fill the gaps at the edge of the cable core to obtain a waterproof and heat-insulating layer (2); S5: The waterproof and heat-insulating layer (2) in S4 is longitudinally wrapped with an aluminum-plastic composite tape and a water-blocking tape to obtain a double-layer water-blocking layer (3); S6: A layer of cross-linked silane halogen-free low-smoke flame-retardant sheath is extruded outside the water-blocking layer (3) in S5.

9. The method for preparing a water-blocking fireproof cable according to claim 8, characterized in that: In step S2, the thickness of the ceramic silicone rubber insulation is not less than 1.0 mm, and the thickness of the ceramic silicone rubber composite tape is 0.2 mm; In step S3, the cable twisting pitch is controlled to be 22 to 26 times the cable outer diameter, and the cores are twisted tightly and not loose; In step S6, the cross-linked silane halogen-free low-smoke flame-retardant sheath is not less than 2.0 mm.

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